1. Adenine and thymine are connected by double hydrogen bonds, and guanine and cytosine are connected by triple hydrogen bonds. Adenine and Guanine are called purines; thymine and cytosine are called pyramidines.
2. DNA grows from 5' - 3'!
DNA REPLICATION
3. To replicate, the double helix of the DNA is unwound and separated to expose two template strands for the new nucleotides to attach to. The result is two identical daughter strands.
4. In replication, the leading strand (3' - 5' into the fork) continuously elongates, whereas the lagging strand (5' - 3') has to be elongated in short fragments called the okazaki fragments.
DNA TRANSCRIPTION
5. DNA transcription starts 5'TATA3' (promotor) and ends at AAUAA (terminator) on the coding strand, using the RNA Polymerase II.
6. Noncoding segments in the pre-mRNA called introns are spliced out by spliceosomes which contain snRNP and snRNA. The coding segments, extrons, are then translated into amino acid sequences.
7. The 5' end is capped with 5' cap (guanine) and the 3' end is capped with poly A tail (adenine) for protection.
DNA TRANSLATION
8. tRNA carries amino acids to the ribosome to be attached to the growing polypeptide chain.
9. Translation always starts with 5'AUG3' (Met) and ends at either UAA, UAG, or UGA.
10. tRNA reads mRNA 3 base pairs at a time (codon), but ONLY after 5'AUG3' is located.
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